1. Field of the Invention
This invention pertains to opthalmic examining apparatus and, more particularly, to apparatus for the self-examination of the human eye which enables a patient to view various conditions of the patient's eye.
2. Description of the Related Art
Various devices have been used to enable doctors to inspect and analyze infirmities and diseases of the human eye. A serious problem with many of these devices is that eye conditions are observable only to the doctor and the patient must rely upon the skill and judgment of the doctor without any means for observing what the doctor sees.
One solution to this problem is a method and apparatus for ocular self-examination disclosed in U.S. Pat. No. 3,903,870 issued Sept. 9, 1975 to Wolf-Dieter Berndt (the "Berndt System"). The apparatus of the Berndt System is an inexpensive, hand-held device to permit a patient to perform a self-examination of the eye and thereby determine if he or she should seek professional help. The apparatus comprises a pen light with its lens bulb pointed at the inside end of a short length of optical fibre positioned along the optical axis of the lens bulb. A flexible rubber cup extending from the lens bulb end of the pen light envelopes the optical fiber. The device is held by hand in a position horizontal to the ground and pointing at the eye, with the flexible rubber cup contacting the eyeball or eyeball socket so that the outside end of the optical fibre is at the anterior focus of the eye.
If a point source of light is placed along the pupilary axis and at the anterior focus of the human eye, according to Berndt, the light rays correspond to a uniform diffuse radiator of energy which is refracted and collimated in parallel rays by the eye's optics. This phenomenon enables the viewer to see his or her own visual system when the axis of the pin hole is along the viewer's pupilary axis. That is, the viewer can see the condition of his or her eye and readily observe cataracts, scar tissue, burns, lesions, floaters and other eye conditions.
For patients who shy away from placing Berndt's flexible rubber cup in contact with the eye or the eye lashes, it is somewhat difficult to maintain the end of the optical fibre at the anterior focus distance from the eye surface while at the same time centering the emitted light on the pupilary axis of the eye. Even with the flexible rubber cup in contact with the eye holding the pen light in a horizontal position so that the emitted light is projected along the pupilary axis can be difficult.
In U.S. Pat. No. 3,787,112 issued Jan. 22, 1974 to John H. Lyons for Apparatus and Method for the Self-Examination of Certain Conditions of the Eye (the "Lyon's System"), the presence, location and nature of a cataract, retinal damage, scars and injuries can be seen by the patient. Lyon's apparatus comprises a conical housing with an eyepiece at its small end and an illuminated target panel near its larger end. An optical system is positioned adjacent its smaller end comprising negative and positive lens separated by a disc with a large pin hole (7 millimeters). Non-collimated diffused light entering the eye through the eye lens impinges upon the retina. A cataract in the eye lens causes a shadow on the retina and the viewer can perceive the outline of the cataract on the illuminated target panel. So Lyon's System, like Berndt's System, permits the self-examination of the human eye, but with a far more expensive apparatus.